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INDUSTRIAL AND ENGINEERING CHEMISTRY
quent improvement in processibility over that obtained with either material alone. The use of the foregoing mixtures, approximately in the order listed, gave indications of a t least moderate improvement in processibility similar to that obtained ivith sulfur and Captax. Perhaps any one of these combinations could be developed somewhat further and substituted for the sulfur and Captax. SUMMARY
The data indicate that treating GR-S for 5 minutes in the Banbury at 380" F. in the presence of the combinations of crosslinking agents listed will cause improvement in processing and stress-strain properties, equal or superior to those produced by sulfur and Captax together. I n turn, this GR-S polymer, treated with sulfur and Captax, was shown t o be superior to GR-S-60 and to GR-S-BO/GR-S blends in ratios higher than 30/70, after
Effect of
Vol. 41, No. 3
mastication and compounding of the polymers in a hot Banbury a t about 380" F. The properties of the sulfur--Captax crosslinked GR-S closely approached the excellent processibility and excelled the poor stress-strain characteristics of GR-S-60 compounded by milling a t normal temperatures. LITERATURE CITED
(1) G a r v e y , B. S.,Jr., Whitlock, &I. H., and Freese, J. A., Ixn. EXQ. CHEM.,34, 1309 (1942). (2) Juve, A. E., B. F. Goodiich Co., SP-T-62 (May 29, 1945). (3) Reconstruction Finance Corp., Office of Rubber Reserve, Specifications for Govt. SynChetic Rubber. Jan. 1, 1946. RECEIVED October 6, 19.17. Presented before the Division of Rubber Chemistry a t the 112th Meeting of the AMERICAN CHEMICAL SocIErr in h'ew York, S . Y. This investigation was carried out under the sponsorship of the Reconstruction Finance Corporation, Office of Rubber Reserve, in connection with the government's synthetic rubber program.
fate and ane Fer entation
A. 31. BUSWELL, J. F. PAGANO, AND F. W. SOLLB, JR.' University of Illinois, Urbana, I l l . Sodium sulfate in concentrations of 4000 p.p.m. or more makes the methane fermentation of glucose at 55' C. impossible. -4cetic acid, however, can be readily fermented in the presence of as much as 10,000 p.p.m. of either sodium chloride or sodium sulfate at 37' C.
HE use of glucose in rayon spinning baths leads to a waste with as high as 5000 p.p.m. biochcmical oxygen demand, not readily treated by the usual methods because of the high salt concentration, and potentially a source of odor nuisance due to reduction of sulfate to hydrogen sulfide under septic conditions. The Ameiican T'iscoee Corporation was confronted with the problem of treating such a waste, and the anaerobic methane fermentation was considered as a possible method. Resistance of this waste to such treatment led to a general study of the effect of salt concentrations on the methane fermentation. APPARATUS
As a first step it was necessary to design a small fermentation apparatus so that several salt concentrations could be tested simultaneously uith the incubator space available. The digester commonly used in this laboratory consists of an inverted 2- or 4-liter filtering flask, fitted with appropriate glass and rubber connections for feeding, sampling, and gas withdrawal ( 2 , 3 ) . The gas outlet is connected to a brine-displacement gasometer of 2- or 3-gallon capacity. The u s d laboratory incubator will house only t n o fermentations if carried out in apparatus of this size, even though the gasometer is placed outside with connections running through the wall of the incubator. The new digester (Figure 1) consists of a 250-ml. extraction flask, with a brine-displacement gasometer fastened above the digester. -4glass tube, 14 nim. outside diameter and 10 mm. long, is sealed to the side of the flask. This is closed with a serum stopper, through vihich, by means of a hypodermic syringe, samples m e taken and additions are made. Fitted with stoppers and a itube for gas flow, a calibrated tube, 48 mm. in outside diameter, is 1
Present address, Nalronai Aluminate Corporation, Chicago, Ill.
fastened above the flask. Above this is set another reservoir for the displaced brine. Gas production is observed dire& by the position of t,he brine level in the calibrated tube, and the brine level is easily reset to zero by opening a Day clamp a t the top of the tube and releasing the gas to the air. The digester is operated with an effective volume of 200 ml., and the capacity of the gasometer is roughly 200 ml. The only disadvantage of the apparatus observed in several months' operation is that it is top-heavy, and care must be taken to avoid accidents during manipulation. These digesters could, of course, be constructed on an even smaller scale, if the fermcntations were not carried out on a quantitative basis. This was considered the minimum-volume compatible with accuracy in gas measurement and analysis of t,he medium. Accuracy in gas measurement with this design is + 2 ml., or less than 2y0 when the daily gas production is over 100 ml. Up to 50 ml. of the fermentation medium may be withdrawn daily for analysis without disturbing the fermentation. TREATMEKT OF WASTE
Analysis of the rayon waste was as follows: glucose O.iS%, sulfuric acid 0.77%, zinc sulfate 0.22%, sodium sulfat,e 2.34%: pH 1.5. It n-as evident that the sulfuric acid would have to be neutralized and the zinc concentration greatly reduced before fermentation could be brought about. Excess lime treatment was found t o accomplish both of thcse ends, prccipit,ating most of the sulfuric acid as calcium sulfate which was removed by filtration. The concentration of zinc remaining after various treatments follows: Treatment CaO ( t o pH 10) CaC03 (excess)
P.P.M. Zinc after Settling for 20 min. 2 hr. 3 hr. 30.4 25.5 20.2 20.2 10.2
...
The treated waste still contained 0.14% calcium sulfate and 2.34% sodium sulfate, which made it seem unlikely that fermentation would be successful; but from the standpoint of expense, removal of the sodium sulfate was impossible. Rudolfs (4,6,6 ) had reported a retarding effect of sulfates and chlorides in concen-
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1949
COTTON P L U G
GRADUATIONS
I Figure 1. Diagram of Digester
trations of 500 to 5000 p.p.m., in batch experiments with sludge digestion. However, he stated that, if sufficient time were allowed, digestion proceeded to approximately the same extent as in the controls. Therefore, it was thought worth while to attempt fermentation of the waste. The temperature chosen was 55' C. since the methane fermentation proceeds rapidly at this temperature and the waste was discharged at approximately this temperature. Vigorous cultures were first developed on pure glucose as a substrate, consuming 1.3 grams of glucose per liter per day. The treated waste, to which was added 100 p.p.m. of nitrogen as ammonium hydroxide, was then substituted for the glucose a t a reduced feeding rate. Fermentation proceeded for about 5 days, but after that time the volatile acid concentration ( 1 ) rose sharply and gas production dropped off. After about 10 days of feeding, there was almost no gas formation and very little volatile acid production, an indication of complete inactivation of the culture. Four of these experiments were run with similar results in all cases. An attempt was then made to acclimate cultures to sodium sulfate bj. gradually increasing the concentration. Working as before with pure glucose as substrate, the sodium sulfate concentration was raised in increments of (a) 500 p.p.m. every third day, ( b ) 200 p.p.m. daily, and (c) 100 p.p.m. daily. In all cases the cultures failed when the calculated sodium sulfate concentration reached the range of 4000 to 8000 p.p.m. Sulfate determinations indicated almost complete reduction of the sulfate ion, part of which was found as hydrogen sulfide in the gas and part as a deposit of free sulfur in the digester. This reduction produced high alkalinities, but cultures in which alkalinity was controlled to a narrow range, known to be suitable for the fermentation, gage similar re-
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sults. Alkalinity control was effected by daily introduction of the required amount of medium low in alkalinity. From this work it was concluded that the maximum concentration of sodium sulfate permissible in the methane fermentation was 3000 to4000p.p.m., a t least with dextrose as the substrate and a t a temperature of 55" C. Septic treatment experiments with the waste from American Viscose Corporation also indicated that sodium sulfate concentrations above 4000 to 5000 p.p.m. greatly inhibited bacterial action. A series of dilutions of the waste was inoculated with stale sewage, incubated for 5 days a t room temperature, and analyzed by the permanganate-oxygen-consumed method (1). Only 30 to 40% removal was found until the sodium sulfate concentration was diluted to 4700 p.p.m., where the removal was 53.5%. The break of the curve in this region agrees with the limit found in the continuous fermentation studies. To make the study more general, cultures were developed on acetic acid as substrate; sodium chloride was added to one series and sodium sulfate to another. Six cultures were developed a t 37" C. to the point where they were capable of consuming 1.0 gram of acetic acid per liter per day. The salt concentrations in the digesters were then raised by 100 p.p.m. per day to a total of 1000, 2000, and 3000 p.p.m., respectively. At these concentrations fermentation proceeded smoothly in all cases as shown by gas production and volatile acid concentration. Gas production corresponded to a 95% yield of methane and carbon dioxide from the acetic acid fed. The volatile acid concentration averaged 200 t o 300 p.p.m. No difference could be noted between results obtained before and after the addition of the salts, although there were occasional daily fluctuations. After operating a t these eoncentrations for a month, the concentrations were raised to 4000, 5000, and 6000, respectively. At these concentrations also, fermentation proceeded with no difficulty and the concentrations were again raised. In this way it was found that concentrations of sodium sulfate as high as 10,000 p.p.m. could be tolerated in the mesophilic fermentation of acetic acid. Of three cultures which were operatrd at this concentration, only one failed. The other two were still in good condition after a month a t this concentration. Attempts to raise this concentration resulted in culture failure. The results with sodium chloride paralleled those with sodium sulfate, fermentation proceeding at 10,000 p.p.m. sodium chloride, but failing a t concentrations above this figure. The concentrations a t which fermentation wag attempted were 1000, 2000, 3000, 4000, 5000, 6000, 8000, and 10,000 p.p.m. At each concentration 30-day continuous satisfactory operation was taken as evidence that the fermentation would proceed a t this concentration. The attempts to operate a t 15,000 p.p.m. sodium chloride were unsuccessful, the cultures failing before this concentrrttion was attained. ACKNOWLEDGMENT
The authors express their gratitude to the American Viscose Corporation, and particularly to E. T. Roetman, for preparation of samples of this waste for study and for information and cooperation a t many times. LITERATURE CITED
(1) Am. Public Health Assoc., "Standard Methods for Examination of Water and Sewage," 9th ed., pp. 215-19 (1946). (2) Busn~ell,A. iM.,et al., Illinois State Water Survey, Bull. 32,43 (1939). (3) Neave, S. L., with Buswell, A. M., J . Am. Chem. SOC.,52, 3313 (1930). (4) Rudolfs, Willem, U.S. Pub. Health Repts., 43, 874-81 (1928). ( 5 ) Rudolfs, Willem, and Zeller, P. J. A,, IND. ENO.CHEM., 20,48-50 (1925). (6) Rudolfs, Willem, and Zeller, P. J. .4., Sewage Works J., 4, 771-81 (1932). RECEIVED October 27, 1947. Presented before the Division of W a t e r , ge, and Sanitation Chemistry a t the 111th Meeting of the AMMERICAK I I C A L SOCIETY, Atlantic City, N. J.
